Malaysia says it will co-operate fully with US investigations into a letter, containing anthrax, sent an office of software giant Microsoft in Reno, Nevada.

The letter bore a Malaysian postmark raising suspicions that responsibility might lie there, but on Monday, Prime Minister Mahathir Mohamad said the US had so far not shared any information.

Once we get information, we will investigate

Prime Minister Mahathir Mohamad

And both Mr Mahathir and Foreign Minister Syed Hamid Albar said it was not certain that the anthrax had originated in Malaysia.

There have been a number of outbreaks of anthrax in the US in recent days, and one person has died.

The letter posted from Malaysia contained pornographic pictures, which tested positive for anthrax. Four employees who handled the letter have tested negative for exposure to anthrax while preliminary tests on two other employees are also negative.

Confusion

The letter was originally posted from Reno, Nevada containing a cheque to a Microsoft vendor in Malaysia. It was returned to the Reno office with the pornographic pictures inserted.

The envelope and cheque tested negative for anthrax.

The origin of the anthrax is not clear

Malaysian police said the US had not yet made any request for help.

"We've not even been told of the address, so how are we to proceed?" said acting Kuala Lumpur police chief, Dell Akhbar Khan.

And Mr Mahathir told reporters: "Once we get information, we will investigate. At this moment we don't know anything."

Foreign Minister Syed Hamid Albar said he did not think the anthrax had come from Malaysia.

"I think definitely there is no truth that the thing originates from Malaysia," he told reporters after a meeting with US Trade Representative Robert Zoellick.

"We are not a country that produces anthrax."

Malaysia has backed the US war on terrorism, condemning the 11 September attacks on New York and Washington. But it has called for a stop to the bombing of Afghanistan.

The government has pledged to prosecute anyone shown to be involved in the Nevada anthrax letter.